Partial fatty acid esters of alkitol anhydrides and a dimeric acid, as corrosion inhibitors



mineral oil compositions containing the same.

Ralph I. Gottshall, Willow Grove, and Raymond T. Kern, Jr., Allentown, Pa., assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application December 28, 1953, Serial No. 400,766

16 Claims. (Cl. 252-5 7) This invention relates to chemical compounds and More particularly, the invention relates to the class of acid esters of dimers of dienoic and trienoic acids with partial fatty acid esters of alkitol anhydrides. The compounds of this invention have been found to possess unusually outstanding corrosion inhibiting properties, and they may be advantageously employed in mineral oil compositions without imparting undesirable water emulsification tendencies thereto.

As is well known in the art, straigh or uncompounded mineral oils are often deficient in one or more respects for the particular use to which they are put. For example, a high resistance to rust or corrosion is important for fuels or lubricants which contact metal surfaces in the presence of water. Fuels or lubricants for internal combustion engines and for gas or steam turbines are examples of materials which may desirablyhave incorporated therein additives or improvement agents which impart corrosion inhibiting properties thereto. 7

Failure to provide sufficient resistance to rust or corrosion by a particular mineral oil, fuel or lubricant may result in extensive wear or damage to costly, finely-machined moving parts. In addition, the damaging eifects of rust or corrosion are not necessarily limited to moving parts themselves, since'rust particles may flake off and form deposits elsewhere, thereby causing clogging of conduits, valves, filters, screens, etc. To overcome this and other deficiencies of uncompounded mineral oils, various agents known as addition agents, additives or improvement agents are commonly incorporated in the particular mineral oil to be used.

The compounds of the present invention form extraordinary eflt'ective corrosion inhibitors which may be used as improvement agents or additives for mineral oils and particularly for lubricating oils such as turbine oils, which are required to function in thepresence of water without excessive emulsification, Thecompounds included by the invention are the acid esters of dimeric acids derived from unsaturated fatty acids containing from 6 to 22 carbon atoms and having from,.2 to 3 ethylenic linkages per molecule "with partial esters of fatty acids containing from 12 to 24 carbon atoms and alkitol anhydrides. compounds and mineral oil compositions containing these compounds are also included by the invention.

The acid esters of this invention are the reaction products resulting from the esterification of a dimerized unsaturated fatty acid of the indicated class with the desired partial fatty acid ester of an alkitol anhydride. The ratio of reactants may range from one mol of dimerized acid per mol of partial fatty acid ester up to the numberof mols of dimerized acid that is equal to the number of free hydroxyl groups in the partial fatty acid ester, per mol of partial fatty acid;ester.'

Methods of making the foregoing United States Patent 4 manner and under conventional conditions. Thus. while 2,767,144 Patented Oct. 16,1956

2 esterification may proceed slowly at room temperature, the reaction is normally advantageously accelerated by heating the reactants, usually with refluxing, and/or by the use of conventional esterification catalysts, such as hydrogen chloride, sulfuric acid, or an aromatic sulfonicv acid, such as p-toluenesulfonic acid. The reaction may be driven to substantial completion by removing one of the products of reaction Since the herein disclosed dimeric unsaturated fatty acids, partial esters of alkitol anhydrides, and their reaction products boil at a temperature substantially above the boiling point of water, the reaction conveniently may be driven to completion by removal of the water of esterification by distillation. The removal of water from the reaction mixture may be facilitated by mechanical agitation, or by bubbling an inert gas, such as nitrogen, through the reaction mixture.

By way of illustrating the foregoing process, one, two or three mols of dimerized acid may be esterified with one mol of a partial fatty acid ester containing three free hydroxyl groups, under conventional reaction conditions, with the elimination, respectively, of one, two or three mols of water of esterification, to form, respectively, a mono-, dior tri-acid or a mono-, di-, or tricarboxylic ester of the dimerized acid and the partial fatty acid ester.

If desired, the reaction products of this invention may be prepared by effecting esterification of the reactants in mineral oil solution. This expedient is advantageous in that it prevents localized overheating of the reactants. Moreover, the resulting reaction products are in the form of mineral oil concentrates, the use of which often facilitates solution of the additives in their ultimate vehicles.

The dimerized acids referred to above are dimers, i. e., bimolecular addition products of conjugated or unconjugated dienoic or trienoic fatty acids having from 6 to 22 carbon atoms before dimerization. Dimeric acids derived from dienoic and trienoic fatty acids are wellknown and can be prepared by conventional methods which form no part of this invention.

More particularly, dimerized acids capable of forming the compounds of this invention are prepared from dior trienoic fatty acids having the generic formula where n is an integer of from 5 to 21 and x is 3 or 5. As will be evident, such monomeric acids contain from 6 to 22 carbon atoms and may contain 2 or 3 ethylenic linkages as the ratio of carbon to hydrogen increases,

i. e., as x increases from 3 to 5. Dimerized acids corresponding to the addition products of the foregoing acids therefore may be defined by the generic formula:

where n is an integer .of from 10 to 42 and where x is an even integer of from 6 to 10. These dimeric acids are therefore dibasic or dicarboxylic .acids havingfrom 12 to 44 carbon atoms. j V 7 Representative members of the class of dimerized acids capable of forming the compounds of this invention are dimers of dienoic acids such as sorbic (hexadienoic), linoleic (octadecadienoic), humoceric (nonadecadienoic) and eicosinic (eicosadienoic) acids. Dimers of trienoic acids, for example, linolenic' and eleostearic (octadecatrienoic) acids also'may be used.

a It is not necessary that both of the unsaturated fatty acid molecules of the bimolecular addition product be identical. Dimers of mixed composition such as those obtained by dimerizing mixed dienoic, mixed trienoic or mixed dienoic and trienoic acids such as may be derived from certain naturally occurring drying oils, e. g., linseed oil and soybean oil, are quite satisfactory.

Dienoic and trienoic acids having 18 carbon atoms, es? pecially those having conjugated olefinic linkages, are preferred for reasons of economy of procurement, ease of reaction and the general excellence of the additives prepared therefrom.

The partial esters of alkitol anhydrides and fatty acids adapted for use in the formation of the reaction products of this invention are the reaction products resulting from esterification with the desired fatty acid of at least one, but less than all, of the available hydroxyl groups of an alkitol anhydride. By alkitol anhydride is meant an intramolecular, monoor di-anhydride of a polyhydric alcohol which contains at least 4 carbon atoms and at least 4 hydroxyl groups, or mixtures of said anhydrides. Representative of the class of alkitols are erythritol; pentitols, such as arabitol, xylitol and adonitil; and hexitols such as mannitol, dulcitol and sorbitol, just as the xylitans and sorbitans are representative of the alkitol anhydrides, or alkitans.

Fatty acids capable of forming partial esters of alkitol anhydrides suited to the preparation of the additives of this invention are the fatty acids containing from 12 to 24 carbon atoms. These acids may be saturated or unsaturated, and they may be substituted with groups which do not adversely affect the oil-solubility or corrosion inhibiting properties of the final reaction product. Representative of this group of acids are lauric acid, oleic acid, ricinoleic acid, stearic acid and lignostearic acid.

Partial esters capable of reacting to form the reaction products of this invention include those formed by reacting a fatty acid of the foregoing kind with the desired alkitol anhydride in a molar ratio of at least 1:1, but less than that which would result in neutralization of all of the hydroxyl groups of the alkitol anhydride. The use of mixtures of partial fatty acid esters of alkitol anhydrides is also included within the scope of the invention. Specific examples of partial esters of alkitol anhydrides capable of reacting with dimeric unsaturated fatty acids to form acid esters included within the scope of the invention are xylitan and sorbitan mono-, sesqui-, diand trioleates and stearates. Partialv esters of hexitol anhydrides, i. e., anhydrides of polyhydrie alcohols containing 6 carbon atoms and 6 hydroxyl groups, are preferred.

The partial esters of alkitol anhydrides disclosed herein as well as the method of preparing the same are conventional and form no part of the present invention. Accordingly, they need not be described in detail.

Representative specific examples of acid esters of dimeric acids with partial fatty acid esters of alkitans included in this invention are the monoand polycarboxylic acid esters of dimerized linoleic, linolenic and eleostearic acids with sorbitan and xylitan mono-, sesqui-, diand tri-oleates and stearates. Included within the foregoing representative class of compounds are mono-, di-, and tri-acid dilinoleic mono-, diand tri-esters of sorbitan monooleate, monoand di-acid dilinoleic monoand di-esters of sorbitan dioleate, mono-acid dilinoleic mono-esters of sorbitan trioleate, monoand di-acid dilinoleic monoand di-esters of xylitan monooleate, monoacid dilinoleic mono-esters of Xylitan dioleate, and corresponding acid esters made from dimerized linolenic and eleostearic acids, as Well as those made from partial esters of stearic acid.

The preparation of the class of compounds included by the invention can be further illustrated by the following specific example:

EXAMPLE I An acid ester of a dimeric unsaturated fatty acid and a partial fatty acid ester of an alkitol anhydride was prepared by admixture and' reaction of 428- parts by weight Physical state: viscous liquid Molecular weight (approx) 564 Gravity, API 13.0 Viscosity, SUV, 200 F 597 Flash, 0C, F 510 Fire, 00, F 575 Color, NPA +10 Iodine No., Mod Hanus 83.3 Saponification No 186 Neutralization No 182 Dimer content (approx) percent Trimer and higher (approx) do 12 Monomer (approx) do n 3 The properties of the sorbitan monooleate were as follows:

Molecular weight (approx) 428 Gravity, API 10.1 Sp. gr., 60/60 F 0.999

Lb./gal., 60 F 8.32 Viscosity, SUV, Sec.:

210 108.3 Flash, P-M, "F 400 Flash, OC, "F 410 Fire, 0C, F 450 Pour, F +10 Physical state, room temp Viscous liquid Color, ASTM Union 4.5 Water by distn, percent Nil Carbon residue, Conradson, percent 2.94 Neutralization value ASTM D 97451 T Total acid No 6.15

pH value, glass-calomel electrodes 7.0 Saponification No.:

ASTM D 94-48 T 149.0 Acetyl value, Gulf 433 142 Ash, percent 0.212

The product obtained in the above-described reaction was a clear, viscous liquid containing predominantly mono-acid esters of dimerized linoleic acid and sorbitan monooleate, having the following physical properties:

Gravity, API 13.4 Sp. gr., 60/60 F 0.977 Lb./gal., 60 F 8.13 Viscosity, SUV,.Sec.:

100 F. 9,936 21.0 498 Flash, P-M, "F 425 Pour, F 0 Physical state, room temp Viscous liquid Color, ASTM Union 6.0 Neutralization Value:

ASTM D 974-51 T- Total acid No 70 pH value, glass-calomel electrodes 4.6

The acid esters of other dimerized unsaturated fatty acids and other partial fatty acid esters of alkitol anhydrides are similarly prepared.

To facilitate handling, blending and the like, it is often desirable to utilize a mineral oil solution of the acid esters. Typical concentrates the above-prepared acid esters in a lubricating oil .had the following properties: r

Sorbitan Monooleate-D i1inoleic- Acid Esters (75% Properties I Concentration) Sample Sample No. 1 No. 2

Gravity, API (wide range in gravity)... 18. 17. 5 Viscosity, SUV, See:

100 F i- 3, 026 5, 729 210 F 206 362 Flash, P-M, 360 430 Pour, F--- +5 +5 Color, ASTM Union 3. 75 6. 5 Water by Distn percent trace trace Water, p. p. m., arl Fischer Method 1, 513 Neutralization Value, ASTM D974-52T, Total Acid N 7 51. 53 48; 95 pH Value, Glass-Calomel Electrodes 4.5 5.1

The reaction products resulting from the above-describedprocedure, either alone or in the form of a mineral oilconcentrate, may be incorporated inthe desired vehicle in any conventional manner. -Where the vehicle is a mineral lubricating oil, 'e. g., a turbine oil, the reaction products are employed in a minor proportion, suflicient to confer corrosion inhibiting properties upon the latter. Normally from about 0.1 to about 1.0 percent of the additive by weight of the composition is sufiicient for this purpose,jalthough greater proportions, i. e., up to 2 or 3 percent by weight, are sometimes desirable and can be used. Examples of variousniiineral oils'which can be benefited by the additives of this invention are gasoline, kerosene, distillate and residual fuel oils, motor oils, lubricatinggreases and turbine oils. The invention .further includes mineral oil compositions wherein the solvent constituent isnot employed as a fuel or a lubricant, but merely as a solvent vehicle. Exemplary of this type of composition are light naphtha and similar solvents containing the novel compounds of thisinventionr; Insuch instancesthe compositions find, use in the coating: art, wherebyi metallic articles subject to rust or corrosion are brushed, dipped or sprayed with a composition c0mprising. the solvent vehicle and the additive."Subsequent evaporation of the soiventleaves an adherent, corrosionresisting coating of the additive on the article. As indicated above,*theherein disclosed compounds are highly effective corrosion inhibitors. This property of the compounds of this invention has .been demonstrated by 's ubjectin'g lubricating "oil compositions containing small concentrations of'these additives to standard test procedures ASTM D 665-52 T and ASTM D 94347 T.

These tests are described in detailin the ASTM Standards of Petroleum Products and Lubricants of. 1952 and 1947, respectively. Briefly, Procedure A of ASTM test D 6 65 -52 T'ini'rolves immersion of-a standard steel test rod rdfj 24-hoursin an agitated mixture of distilled water and testfoil maintained-at a temperature of 140 F. The corrosion inhibiting properties ofthe oil can be evaluated by; examinatiomof the steel rod for corrosion -or rust uponcompletidn of 'the test.. ASTM D 94347.T involves'the passage of. oxygen at a measured rate of 3 liters per hour into an oi1 water 'mixturemaintained at 203 F., andgl avingian iron; coil immersed therein. The test is carried out for a predetermined number of hours or until the oil has reached a neutralization number of 2.0. The corrosion inhibitingproperties of the oil can be determined during the test by examination of the iron coil for rust or corrosion.

The corrosion inhibiting properties of the additives of the present invention were markedly superior to those of eitherof the parent compounds as indicated by the data set forth in the following example:

EXAMPLE II To separate samples of a highly refined, highly paraffinic turbine oil base inhibited against oxidation and having an API gravity of between 305 and 32.5 and a viscosity of 150 SUS at F. were added respectively 0.05 percent by weight of dimerized linoleic acid, sorbitan monooleate, and the reaction product prepared in accordance with Example I. These samples together with a sample of the unimproved turbine oil base were subjected to the above-described ASTM tests as indicated. The results of these tests are set forth in the following table:

The compounds of the present invention achieve their beneficial results without at the same time imparting to the oils the undesirable emuision-forming tendencies which normally would be expected from a'knowledgeof the emulsification tendencies conferred upon oils by alkitol anhydrides. This advantage has been demonstrated by subjecting lubricating oils containing small concentrations of the additives of this invention to the standard procedure of Federal Emulsification Test Fed. 320.1.5, described in Federal Specifications VVL79ld, amended 20' June, 1950, 'and'to the standard steam emulsiontest proc'edurefAS TM D 157-51 T. 'Briefly, the Federal Emulsification Testis carried out by agitating a mixture of 40ml. of the tested oil and 40 ml. of distilled water or a'standa'rd aqueous salt solution for 5 minutes. The tendency toward emulsion formation is determined by measuring the number of ml. in the Water layer, in the oil layer and in the emulsion layer, if any, and/ or by observing the time required for/the emulsion to break. The ASTM steam emulsionjt'est is carried out by passing live steam-through a measured sample of the test oil until the volumeofi the condensed steam and oil is double that of the originaloil sample.- The oil and water mixture is then allowed to settle at a temperature of 200-203- F. The number of seconds required for the separation of the original volume of oil is reported as the Steam Emulsion number. i i The water emulsification properties of the additives of this invention are illustrated by the following example:

EXAMPLE 111 Accordingly, examination of Table A indicates that the compounds of the present invention possess decidedly superior corrosion inhibiting properties as compared with either of the materials reacted to form said compounds. Examination of the results set forth in Table B indicates that the compounds of this invention overcome to a large extent the undesirable emulsion-forming tendencies of the partial fatty acid esters of alkitol anhydrides. Similar desirable properties have been demonstrated for various representative acid esters within the disclosed class of compounds, including, for example, di-acid and triacid dilinoleic diand tri-esters of sorbitan monooleate.

It is to be understood that the improved mineral oil compositions of this invention can be additionally improved by incorporation therein of other known additives in order to confer thereon other desirable properties, such as increased resistance to oxidation, increased stability, etc. Thus, there can be added viscosity index improvers, thickeners, bearing corrosion inhibitors, antioxidants, extreme pressure agents, foam inhibitors, detergents, dyes, sludge inhibitors, etc.

The reaction products included by the invention also find utility as corrosion-inhibiting additives for various paints, varnishes, automobile undercoatings and the like. In the use of the agents of this invention in the abovedescribed coating compositions, it maybe desirable to employ these agents in substantially greater concentrations than are normally utilized in fuels and lubricants.

It will be understood by those skilled in the art that numerous modifications may be resorted to without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. An acid ester of (1) a dimeric acid derived from an unsaturated fatty acid containing from 6 to 22 carbon atoms and having from 2 to 3 ethylenic linkages per molecule and (2) a partial ester of a fatty acid containing from 12 to 24 carbon atoms and an alkitol anhydride containing 4 to 6 carbon atoms, said acid ester containing at least 1 unreacted carboxyl group per molecule.

2. An acid ester of (1) a dimeric acid derived from an unsaturated fatty acid containing 18 carbon atoms and having from 2 to 3 ethylenic linkages permolecule and (2) a partial ester of a fatty acid containing 18'carbon atoms and a hexitol anhydride, said acid ester containing at least 1 unreacted carboxyl group per molecule.

3. An acid ester selected from the group consisting of mono-, di-, and tri-acid esters of a dimer of linoleic acid and sorbitan monooleate.

4. A mono-acid ester of dilinoleic acid and sorbitan monooleate.

5. A di-acid ester of dilinoleic acid and sorbitan monooleate.

6. A tri-acid ester of dilinoleicacid and'sorbitan monooleate.

7. A method of preparing an acid ester of a dimerized unsaturated fatty acid and a partial ester of an alkitol anhydride, which acid ester contains at least 1 unreacted carboxyl group per molecule, said method comprising esterifying a dimeric acid derived from an unsaturated fatty acid containing from 6 to 22 carbon atoms and having from 2 to 3 ethylenic linkages per molecule with a partial ester of a fatty acid containing from 12 to 24 carbon atoms and an alkitol anhydride containing 4 to 6 carbon atoms, in a mol ratio of at least one mol of dimeric acid per mol of partial ester, and continuing the reaction until approximately 1 mol of water of esterification per mol of reacted dimeric acid has been produced.

8. A mineral oil composition comprising a major amount of a mineral oil and a minor amount, sufiicient to impart corrosion inhibiting properties to the composition, of an acid ester of 1) a dimeric acid derived from an unsaturated fatty acid containing from 6 to 22 carbon atoms and having from 2 to 3 ethylenic linkages per molecule and (2) a partial ester of a fatty acid containing from 12 to 24 carbon atoms and an alkitol anhydride containing 4 to 6 carbon atoms, said acid ester containing at least 1 unreacted carboxyl group per molecule.

9. The composition of claim 8 wherein the mineral oil is a lubricating oil.

10. The composition of claim 8 wherein the mineral oil is a turbine oil.

11. A lubricating oil composition comprising a major amount of a mineral lubricating oil and a minor amount, sufficient to impart corrosion inhibiting properties to the composition, of an acid ester of (1) a dimeric acid derived from an unsaturated fatty acid containing 18 carbon atoms and having from 2 to 3 ethylenic linkages per molecule and (2) a partial ester of a fatty acid containing 18 carbon atoms and a hexitol anhydride, said acid ester containing at least 1 unreacted carboxyl group per molecule.

12. A lubricating oil composition comprising a major amount of a mineral lubricating oil and a minor amount, sufficient to impart corrosion inhibiting properties to the composition, of an acid ester selected from the group consisting of mono-, di-, and tri-acid esters of a dimer of linoleic acid and sorbitan monooleate.

13. The composition of claim 12 wherein said acid ester is present in the composition in an amount of from about 0.01 to about 1.0 per cent by weight of the composition.

14. The composition of claim .12 where the acid ester is a mono-acid ester of dilinoleic acid and sorbitan monooleate.

15. The composition of claim 12 where the acid-ester is a di-acid ester of dilinoleic acid and sorbitan monooleate.

16. The composition of claim 12 where the acid ester is a tri-acid ester of dilinoleic acid and sorbitan monooleate.

References Cited in the file of this patent UNITED STATES PATENTS 2,398,193 Sharp Apr. 9,194.6 2,495,305 Wyler Jan. 24, 1950 2,563,609 Matuszak Aug. 7, 1951 2,590,911 Wittcoff Apr. 1, 1952 2,623,887 Matuszak Dec. 30, 1952 2,631,979 McDermott Mar. 17, 1953 2,632,695 Landis et al Mar. 24, 1953 FOREIGN PATENTS 428,864 Great Britain May 15, 1935 

1. A ACID ESTER OF (1) A DIMERIC ACID DERIVED FROM AN UNSATURATED FATTY ACID CONTAINING FROM 6 TO 22 CARBON ATOMS AND HAVING FROM 2 TO 3 ETHYLENIC LINKAGES PER MOLECULE AND (2) A PARTIAL ESTER OF A FATTY ACID CONTAINING FROM 12 TO 24 CARBON ATOMS AND AN ALKITOL ANHYDRIDE CONTAINING 4 TO 6 CARBON ATOMS, SAID ACID ESTER CONTAINING AT LEAST 1 UNREACTED CARBOXYL GROUP PER MOLECULE. 